Aneurysms are spindle-shaped or sack-shaped localized permanent expansions of the cross-section of arterial blood vessels which occur as a result of congenital or acquired changes of the vessel wall. With what are referred to as true aneurysms (aneurysm verum) the entire diseased vessel wall is expanded, whereas with false aneurysms (aneurysm falsum or spurium) the cause lies in a split in the vessel wall. Aneurysms represent a significant risk for the patient, since in the case a rupture (i.e. a tearing outwards or inwards of the aneurysms) serious damage which may even be fatal can occur.
As a rule the causes of aneurysms are degenerative diseases of the vessel wall, in rare cases traumas, infections such as rheumatic fever, inflammations or a congenital weakness of connective tissue (Marfan syndrome, Ehlers-Danlos syndrome). In around 5 to 7% of aneurysms, these occur at multiple different places in the body. Aneurysms of the aorta can be of clinical significance not just for adults but also as a result of a Marfan syndrome or as late effects of a volume stress of the aorta with congenital heart defects with right-left shunt or a shunt-dependent perfusion of the lungs. Furthermore diseases in the Kawasaki syndrome can result in aneurysms on the coronary blood vessels.
To treat brain aneurysms there is the option of an endovascular or a neurosurgical treatment. In an endovascular therapy so-called coils, which involve spirals made of a platinum alloy, are brought into the aneurysm sack. These fill about 30% of the aneurysm and cause the formation of a thrombosis which prevents further blood circulation in the aneurysm. This means that a rupture, i.e. a tearing away, is no longer possible. In addition many further forms of therapy are possible, e.g. gluing etc.
With neurosurgical therapy on the other hand, which requires an open operation on the brain, the aneurysm is treated within the framework of a craniotomy. The aneurysm sack is clamped off with the aid of a clip, made of Titanium for example. In this way the aneurysm is cut off from the blood circulation. Alternatively the aneurysm can be wrapped, meaning that the artery aneurysm wall is strengthened.
The aneurysms which arise for example from a congenital weakness of the cells of the vessel inner wall (endothel cells) preferably occur at branches in vessels. Since at the intracranial arteries the muscle layer is thinner than at the other arteries of the body, the brain base vessels are predisposed to the occurrence of aneurysms. In autopsies aneurysms which have not bled are found in around 1 to 5% of the population. In women they occur more frequently than in men.
Aneurysms at the brain base vessels can cause fatal bleeding in they brain if they rupture. In such a case mortality rates are around 60 to 70%. In addition it is extremely probable that after such bleeding in the brain neurological incapacities such as paralysis, loss of speech and brain damage remain.
Therefore it is unavoidable in many cases that an aneurysm is treated, in order not to expose the patient to the danger of a rupture, i.e. a tearing of the aneurysm, with the consequences described. Intervening with an aneurysm however represents an intervention fraught with risk which is not induced with “stable” aneurysms and thus represents a danger without medical benefit for the patient. In addition such interventions are associated with high costs.
Thus the risk of such an intervention must be carefully balanced against the danger. In order to enable the decision for or against an intervention to be made, it is of greatest interest to be able to recognize the danger of rupture for an aneurysm, in order to be able to include this as a basis for making the decision.
It is currently the case that all aneurysms that have exceeded a certain threshold value of their diameter are treated. In addition anatomical circumstances are considered to a slight extent. The actual risk of rupture can only be assessed very inexactly on the basis of this data.